Thermal management of an electrochemical engine presents several important considerations and challenges as compared to a conventional internal combustion engine. First, in an internal combustion engine, waste heat is managed about equally through both an exhaust gas stream and through a flow of air-cooled engine coolant. In comparison, an electrochemical engine manages most of its waste heat through air-cooled engine coolant. Second, an internal combustion engine typically operates at 120° C., where an electrochemical engine operates at the lower temperature of 80° C. Therefore, the heat transfer between the coolant and air in a thermal management system of an electrochemical engine is about one-half that of an internal combustion engine due to the smaller temperature differential between the waste heat and ambient at 38° C. These two considerations in combination may necessitate a threefold increase in the cooling airflow rate through the radiator and an order of magnitude increase in its associated fan power.
The cooling requirement has generally been met by placing a large radiator at the front of the vehicle. However, due to the current size of the radiator, vehicle style has been strongly driven by the high rate of airflow required for cooling. Although some reduction of heat rejection requirements is achieved through higher thermodynamic efficiencies of the electrochemical engine, there is a continued need for creative cooling solutions for vehicle applications where space is limited.